1. Field of the Invention
The invention relates to an electro-optical display formed by a pair of planar electrode coated parallel plates between which is disposed a display medium.
2. Description of the Prior Art
Such an elecro-optical display is known from German Offenlegungschrift No. 2,655,166.
Conventional reflective display, such as, say, liquid crystal displays, frequently lose their brightness and hence readability in an unacceptable way as soon as they are mounted vertically and are read, in that position, by an observer, whose eyes are usually at approximately the height of the display. The reason for this abrupt loss of brightness of the conventional reflective displays resides in the fact that these displays in general only possess a planar, mirror-like or slightly diffuse relfector without special structure, and this type of relfector reflects the light, which in general is incident from above, onto the ground instead of towards the observer.
Proposals as to how, in quite specific types of displays, light incident from above could be redirected into the eye of the observer are known from German Offenlegungsschrift No. 2,512,548, U.S. Pat. No. 3,768,887 and U.S. Pat. No. 3,838,909. However, all these solutions are based on types of displays which must possess, at the top, an additional, horizontal window for the entry of light. However, such a window, together with the frequently involved path of the beam, and the partly space-consuming reflectors and deviating plates, prevents a flat construction of the display. For this reason, such solutions are out of the question for a modern display, where flat, space-saving displays are always demanded.
German Offenlegungsschrift No. 2,655,166 discloses a solution by means of which electro-optical displays can be constructed without an additional horizontal window for the incident light. However, it is a disadvantage of this solution that because of the prism deviating plate required at the front of the display, the front again requires more space. Further it should be mentioned, in connection with this solution, that a front plate of this type, provided with prisms, undoubtly suffers rapid soiling and can easily cling and suffer abrasion.